Poly(arylene ether) dielectrics

ABSTRACT

The present invention relates to poly(arylene ethers) used as low k dielectric layers in electronic applications and articles containing such poly(arylene ethers) comprising the structure: 
                 
 
wherein n=5 to 10000 and monovalent Ar 1  and divalent Ar 2  are selected from a group of heteroaromatic compounds that incorporate O, N, Se, S, or Te or combinations of the aforesaid elements, including but not limited to:

FIELD OF THE INVENTION

The invention relates to the field of dielectric materials. Moreparticularly, the present invention is directed to poly(arylene ethers)containing pyridine and thiophene moieties used as low dielectricinsulating layers in electronics applications and articles containingsuch poly(arylene ethers).

BACKGROUND OF THE INVENTION

Microelectronics fabrication involves the manufacture of integratedcircuits which uses dielectric materials as insulating layers betweenvarious circuits and layers of circuits. As the device dimensions ofadvanced microelectronics integrated circuits continue to shrink, theincrease in propagation delay, capacitance coupling between two or moreconductive features and power dissipation of the interconnect structurebecome significant limiting factors.

The capacitance between two or more conductive features is proportionalto the dielectric constant, k, of the material which separates thefeatures. These features are usually vias for vertical connectionsbetween layers and trenches for horizontal connections within a layer. Adielectric material with a low k value is desirable in reducing thetendency for higher capacitance coupling when conductive features arebrought closer together in more advanced circuit designs.

Silicon dioxide which has been typically used as a dielectric materialin the microelectronics fabrication industry has a k value of about 4.There is a need for new dielectric materials with a k value below 3. Amethod of lowering the dielectric constant of silicon oxide is describedin U.S. Pat. No. 6,147,009 where a hydrogenated oxidized silicon carbonmaterial (SiCOH) is formed in a chemical vapor deposition (CVD) chamber.Another low k material comprised of carbon doped silicon oxide that isdeposited by a CVD method is described in U.S. Pat. No. 6,303,523. Tosuccessfully replace silica as a dielectric material, a polymericmaterial must have a thermal stability to at least 350° C. which is atypical temperature at which dielectric films are cured if they are spincoated on a substrate.

U.S. Pat. No. 6,280,794 discloses a method of forming dielectricmaterial with a low k value by forming pores within a dielectricpolymer. The pores contain air with a dielectric constant of 1 whichreduces the k value of the two phase film proportional to the volumefraction of air in the polymer film.

U.S. Pat. Nos. 5,874,516 and 5,658,994 disclose poly(arylene ethers)which do not contain any functionalized or reactive groups in thepolymer. The utility of these polymers is recited to be for lowdielectric insulating layers in integrated circuits and articlescontaining such poly(arylene ethers).

A trend in the microelectronics fabrication industry is to replace thecurrent conductive material which is aluminum with lower resistivitymaterials such as copper. Copper or copper ions that diffuse away fromthe conductive feature can reduce the performance of the device. Adielectric material that has the additional property of being able totrap copper or copper ions and prevent them from diffusing is highlydesirable. F. Cotton and G. Wilkinson in “Advanced Inorganic Chemistry”published by Interscience Publishers (1966), page 896 write that cuprouscomplexes of pπ bonding ligands are known. Aromatic compounds with alone pair of electrons like pyridine or thiophene are capable of formingπ complexes with metals through their p orbitals.

SUMMARY OF THE INVENTION

An objective of the present invention is to provide a low k dielectricmaterial in which k is less than 3 for the fabrication of integratedcircuits in electronic or microelectronic devices.

A further objective is that said low k dielectric material has a thermalstability of about 350° C. or greater after curing on a substrate.

A still further objective is that said dielectric layer traps copper orcopper ions to prevent undesirable diffusion from a conductive layerthrough the dielectric layer to other parts of the device.

These objectives are achieved by the present invention which offers animproved dielectric material. More particularly, the dielectric materialis a poly(arylene ether) comprising the structure:

wherein n=5 to 10000; and monovalent radical Ar₁ and divalent radicalAr₂ are selected from the group of heteroaromatic compounds thatincorporate O, N, Se, S, or Te or combinations of the aforesaid elementsincluding but not limited to:

In one embodiment, the dielectric material of the present invention isformed as a cap layer on a dual or single damascene structure. The low kdielectric material is dissolved in an organic solvent and spin coatedon a substrate followed by baking to cure the film and form a stablelayer.

In another embodiment, the dielectric material is provided betweendielectric layers (insulating layers) in an integrated circuit andfunctions as an etch stop layer in a damascene structure. The low kdielectric material is spin coated from a solution and then baked toremove solvent and cure the film.

More preferably, the dielectric layer is provided between two conductivelayers in an integrated circuit. More particularly, the dielectricmaterial is an intermetal dielectric in a dual or single damascenestructure.

The present invention is also a multilayer microelectronic integratedcircuit article comprising (i) a silicon, glass, silicon-germanium, orceramic substrate, (ii) one or more layers of a conductive materialcontained within or on said substrate; and (iii) one or more dielectriclayers contained within or on said substrate, at least one of saiddielectric layers comprised of a poly(arylene ether) having thestructure:

wherein n=5 to 10000; and monovalent radical Ar₁ and divalent radicalAr₂ are selected from the group of heteroaromatic compounds thatincorporate O, N, Se, S, or Te or combinations of the aforesaid elementsincluding but not limited to:

The poly(arylene ether) structures described above will hereafter bereferred to as poly(arylene ether) I for purposes of clarification.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2 are cross sectional views of a dual damascene structurehaving a low k dielectric material of the invention in one or morelayers.

FIG. 3 is a cross sectional view of a single damascene structureincluding low k dielectric materials of the invention in one or morelayers.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a dielectric material provided (i) asan insulating layer between conductive layers in an integrated circuit,(ii) as an etch stop layer between insulating layers in an integratedcircuit, or (iii) as a passivation layer between a conductive layer andan insulating layer in an integrated circuit.

With specific reference to devices featuring dual damasceneinterconnects as depicted in FIG. 1, the poly(arylene ether) 1 of thepresent invention can function a a dielectric material in one or more ofthe following parts of the interconnect structure: intermetal dielectriclayers 150 and 170 which are adjacent to the conductor metal 130;passivation layer 120 which is on the conductive layer 110 and onsubstrate 100; etch stop layer 160; and cap (etch stop) layer 140. Notethat poly(arylene ether) 1 is described in a separate embodiment in alater section and may be used interchangeably with poly(arylether) 1.

In one embodiment, a substrate 100 is provided in which a conductivelayer 110 has been formed. Substrate 100 is typically silicon orsilicon/germanium and should be understood to possibly include one ormore active devices, one or more passive devices, and one or moredielectric layers in a substructure (not shown). Conductive layer 110 isimbedded in a dielectric layer which is not shown in order to simplifythe drawing and direct attention to the key features of the presentinvention. Conductive layer 110 is comprised of a material like copperor a copper alloy, tungsten or a tungsten alloy, or aluminum or analuminum alloy.

A passivation layer 120 comprised of poly(arylether) 1 is formed by spincoating a solution of poly(arylene ether) 1 on substrate 100 and onconductive layer 110 followed by baking to cure the film. Films orcoatings of the poly(arylene ether) 1 can be formed by spin coating orspraying, with spin coating preferred. Preferred solvents fordissolution of the polymer include cyclohexanone, cyclopentanone,chloroform, toluene, xylene, chlorobenzene, N,N-dimethylformamide,methyl isobutyl ketone, N-methyl pyrrolidinone and mixtures thereof.Additives such as stabilizers, surfactants and the like can be added toimprove shelf life stability of the polymer in solution or to enhanceits film forming properties. Adhesion promoters may be used to improveadhesion of the poly(arylene ether) 1 to the substrate. Typically, thefilms are spun to a thickness of between 1000 and 15,000 Angstroms. Itis preferred that baking between 50° C. and 250° C. for a period ofbetween 0.5 and 30 minutes followed by curing (in furnace or rapidthermal annealing) between 200° C. and 400° C. for a period of between 5and 120 minutes should take place after spin coating. Passivation layer120 protects conductive layer 110 from chemicals and etchants used insubsequent processes employed to form a via hole and trench.

Next a dielectric layer 130 is deposited preferably by a CVD method. Thedielectric layer is comprised of a material such as SiO₂, carbon orfluorine doped silicon oxide, polysilsesquioxanes, borosilicate glass,borophosphosilicate glass, and polyimide. Optionally, an organicmaterial such as FLARE from Allied Signal or SILK from Dow Corning maybe spin coated and cured by baking to form a dielectric layer 130.

An etch stop layer 140 is then formed on dielectric layer 130 by spincoating and curing poly(arylene ether) 1 by the same process asdescribed for passivation layer 120. Optionally, an etch stop materialsuch as silicon nitride, silicon carbide, or silicon oxynitride may bedeposited instead of the poly(arylene ether) 1.

A second dielectric layer 150 is then deposited by a CVD technique orthe like and is selected from the same candidates as mentioned fordielectric layer 130. Then a dielectric cap layer 160 that serves as anetch stop layer for a subsequent chemical mechanical polish step isdeposited. Cap layer 160 is comprised of poly(arylene ether) 1 that isformed by spin coating and baking processes described for passivationlayer 120. Optionally, a material such as silicon nitride, siliconcarbide, or silicon oxynitride may be deposited as cap layer 160.

Conventional photolithography and etch processes are employed to form avia hole 170 and a trench 180 as shown in FIG. 1. A barrier metal layer185 is deposited on the sidewalls and bottom of via 170 and trench 180by a CVD method and is comprised of a material such as Ta, Ti, W, TaN,TiN, WN, TiW, or TaSiN. Barrier metal layer 185 is intended to preventmetal diffusion from the interconnect into the adjacent dielectric andetch stop layers and also protects the metal within the interconnectfrom moisture or other agents in an adjacent dielectric or etch stoplayer that might attack said metal. A metal layer 200 is then depositedby electroplating, evaporating, or sputtering to fill via 170 and trench180. The metal layer 200 is selected from the same set of materials thatwere mentioned previously as candidates from conductive layer 110. Sincethe deposition process provides a metal layer 200 that extends above caplayer 160, a CMP step is used to lower the level of metal layer 200until it is contained only within via 170 and trench 180 and is coplanarwith the top of cap layer 160.

By serving as one or more etch stop layers and as a cap layer in thedual damascene structure illustrated in FIG. 1, poly(arylene ether) 1with its low k dielectric constant is able to reduce the capacitivecoupling between metal wiring and improve the performance of the device.Note that alternative materials such as silicon nitride and siliconoxynitride have higher k values and are not as effective in preventingcapacitive coupling.

In a second embodiment, a substrate 210 is provided in which aconductive layer 220 has been formed as shown in FIG. 2. Substrate 210is typically silicon or silicon/germanium and should be understood topossibly include one or more active devices, one or more passivedevices, and one or more dielectric layers in a substructure (notshown). Conductive layer 220 is imbedded in a dielectric layer which isnot shown in order to simplify the drawing and direct attention to thekey features of the present invention. Conductive layer 220 is comprisedof a material like copper or a copper alloy, tungsten or a tungstenalloy, or aluminum or an aluminum alloy. A passivation layer 230comprised of a material such as silicon nitride, silicon carbide orsilicon oxynitride is deposited on substrate 210 and on conductive layer220 by a CVD technique.

Next a dielectric layer 240 is formed by spin coating a solution ofpoly(arylene ether) 1 followed by baking to cure the film. Films orcoatings of the poly(arylene ether) 1 can be formed by spin coating orspraying, with spin coating preferred. Preferred solvents fordissolution of the polymer include cyclohexanone, cyclopentanone,chloroform, toluene, xylene, chlorobenzene, N,N-dimethylformamide,methyl isobutyl ketone, N-methyl pyrrolidinone and mixtures thereof.Additives such as stabilizers, surfactants and the like can be added toimprove shelf life stability of the polymer in solution or to enhanceits film forming properties. Adhesion promoters may be used to improveadhesion of the poly(arylene ether) 1 to the substrate. Typically, thefilms are spun to a thickness of between 1000 and 15,000 Angstroms. Itis preferred that baking between 50° C. and 250° C. for a period ofbetween 0.5 and 30 minutes followed by curing (in furnace or rapidthermal annealing) between 200° C. and 400° C. for a period of between 5and 120 minutes should take place after spin coating.

An etch stop layer 245 is then deposited and selected from the samegroup of materials as described for passivation layer 230. A seconddielectric layer 250 is formed with the same material and technique asused to apply dielectric layer 240. The damascene stack is completed bydepositing cap layer 255 which is also selected from the same group ofmaterials as mentioned for passivation layer 230 and etch stop layer245. Conventional photolithography and etch processes are employed toform a via hole 260 and trench 270 in the damascene stack. A barrierlayer 280 comprised of Ti, Ta, W, TiN, TaN, WN, TiW, or TaSiN or asimilar material that is deposited on the sidewalls and bottom of via260 and trench 270. Barrier layer 280 is intended to prevent metaldiffusion from the interconnect into adjacent dielectric and etch stoplayers and also protects the metal within the interconnect from moistureor other agents in an adjacent dielectric or etch stop layer that mightattack said metal. A metal layer 290 is then deposited byelectroplating, evaporating, or sputtering to fill via 260 and trench270. The metal layer 290 is selected from the same set of materials thatwere mentioned previously as candidates from conductive layer 220. Sincethe deposition process provides a metal layer 290 that extends above caplayer 255, a CMP step is used to lower the level of metal layer 290until it is contained only within via 260 and trench 270 and is coplanarwith the top of cap layer 255.

As dielectric layers 240, 250 in the dual damascene structureillustrated in FIG. 2, poly(arylene ether) 1 with its low k dielectricconstant is able to reduce the capacitive coupling between metal wiringand improve the performance of the device. Since poly(arylene ether) 1in dielectric layers 240, 250 has a thermal stability about 350° C. orgreater, the dielectric layer is able to remain in the device as apermanent layer. Furthermore, dielectric layers 240, 250 have an addeddesirable feature in that they contain heteroaromatic functionality thatcan complex with metals such as copper and prevent them from diffusingthrough insulating layers and degrading the performance of the resultingdevice.

With specific reference to devices featuring single metal interconnectssuch as the single damascene structure shown in FIG. 3, poly(aryleneether) 1 can function as a passivation layer 320 which is on theconductive layer 310 and on substrate 300; as a cap layer 340, orpreferably as an intermetal dielectric layer 330.

In a third embodiment, a substrate 300 is provided in which a conductivelayer 310 has been formed. Substrate 300 is typically silicon orsilicon/germanium and should be understood to possibly include one ormore active devices, one or more passive devices, and one or moredielectric layers in a substructure (not shown). Conductive layer 310 isimbedded in a dielectric layer which is not shown in order to simplifythe drawing and direct attention to the key features of the presentinvention. Conductive layer 310 is comprised of a material like copperor a copper alloy, tungsten or a tungsten alloy, or aluminum or analuminum alloy. A passivation layer 320 comprised of a material such assilicon nitride, silicon carbide, or silicon oxynitride is deposited onsubstrate 300 and on conductive layer 310.

Next a dielectric layer 330 is formed by spin coating a solution ofpoly(arylene ether) 1 followed by baking to cure the film. Films orcoatings of the poly(arylene ether) 1 can be formed by spin coating orspraying, with spin coating preferred. Preferred solvents fordissolution of the polymer include cyclohexanone, cyclopentanone,chloroform, toluene, xylene, chlorobenzene, N,N-dimethylformamide,methyl isobutyl ketone, N-methyl pyrrolidinone and mixtures thereof.Additives such as stabilizers, surfactants and the like can be added toimprove shelf life stability of the polymer in solution or to enhanceits film forming properties. Adhesion promoters may be used to improveadhesion of the poly(arylene ether) 1 to the substrate. Typically, thefilms are spun to a thickness of between 1000 and 15,000 Angstroms. Itis preferred that baking between 50° C. and 250° C. for a period ofbetween 0.5 and 30 minutes followed by curing (in furnace or rapidthermal annealing) between 200° C. and 400° C. for a period of between 5and 120 minutes should take place after spin coating.

A cap dielectric layer 340 that also functions as an etch stop layer fora subsequent CMP step is then deposited on dielectric layer 330. Caplayer 340 is selected from the same group of materials as described forpassivation layer 320. An opening 350 such as a trench or contact holeis then formed in cap layer 340 and in dielectric layer 330 byconventional photolithography and etch processes. Optionally, a barriermetal layer 360 comprised of a material such as Ti, Ta, W, TiN, TaN, WN,TiW, or TaSiN is deposited on the sidewalls and bottom of opening 350. Ametal layer 370 is deposited to fill opening 350 and the deposition isfollowed by a CMP step to planarize metal layer 370 so that it iscontained within opening 350 and becomes coplanar with the top of caplayer 340. Dielectric layer 330 comprised of poly(arylene ether) 1 withits low k dielectric constant is able to reduce the capacitive couplingbetween metal wiring and improve the performance of the device. Sincepoly(arylene ether) 1 in dielectric layer 330 has a thermal stability ofabout 350° C. or greater, the dielectric layer is able to remain in thedevice as a permanent layer. Furthermore, dielectric layer 330 has anadded desirable feature in that said layer contains heteroaromaticfunctionality that can complex with metals like copper and prevent themfrom diffusing through insulating layers and degrading the performanceof the resulting device.

The present invention is also a composition comprised of a poly(aryleneether) 1 comprising the structure:

wherein n=5 to 10000; and monovalent radical Ar₁ and divalent radicalAr₂ are selected from heteroaromatic groups that incorporate O, N, Se,S, or Te or combinations of the aforesaid elements including but notlimited to:

The polymers described herein have low k values and good thermalstability and have the additional property of being able to trap metalsor metal ions that diffuse away from the conductive feature. Thisdiffusion would otherwise limit device performance. The poly(aryleneethers) of the present invention can also be used as coatings,dielectric layers, encapsulants, barrier layers or substrates inapplications not limited to microelectronic devices, including but notlimited to integrated circuits and multichip modules, printed circuitboards, and photodiode arrays.

The poly(arylene ethers) of the present invention are prepared in highmolecular weight by proper modification of the Ullmann ethercondensation polymerization as described in Example 1. Ullmann ethercondensation reaction uses copper catalyst. The nucleophilic aromaticsubstitution reaction is facilitated by cuprous ion. The solvent used inthe polymerization is not critical as long as it is inert and is asolvent of the polymer that is formed. Hence the polymerization in thepresent invention uses cuprous salt as the catalyst and benzophenone asthe solvent. The cuprous salt employed in the reaction is a cuproushalide. Cuprous halides are preferred since they are highly effectivebut other cuprous salts can also be employed.

As the Ullmann ether reaction requires high temperatures, thetemperature used in the present invention is between 170° C. and 220° C.for a period of 40 to 48 hours. The optimum polymerization temperatureand time depends upon the monomer used. The synthesis of the polymerinvolves monomers with dihydroxyl and dihalogenated aromatic units. Thepolymer of the present invention is prepared preferably with equal molarequivalents of the alkaline metal salt of dihydroxyl aromatic unit anddihalogenated unit.

The alkaline salt of the dihydroxyl aromatic unit can be prepared usingalkaline metal, alkaline metal hydroxide, or alkaline metal hydride.This alkaline salt can be prepared separately or just before thepolymerization steps.

The polymer obtained from the reaction can be recovered by anyconvenient manner, such as precipitation induced by cooling the reactionmass, by pouring the reaction mixture into a non-solvent, or bystripping off the solvent in the reaction mixture at reduced pressureand/or elevated temperature.

Since the polymerization reaction results in formation of an alkalinemetal halide, it is preferred that the alkaline metal halide be removedby filtering the salt from the polymer solution or by Soxhlet-extractingthe polymer to substantially free if from this salt.

The polymerization reaction described above was used to prepare threepolymers whose dielectric constant (k), glass transition temperature(Tg), and decomposition temperature are listed in Table 1. Structures ofthe polymers are shown in Table 2.

TABLE 1 Properties of Poly(arylene ethers) 1a-1c 1a 1b 1c Dielectricconstant ˜2.43 ˜2.65 ˜2.35 Decomposition temperature 310 345 450 (inair)/° C. Decomposition temperature 355 325 450 (in nitrogen)/° C. Glasstransition temperature/ 312 214 227 ° C. Molecular weight ˜25,000˜11,000 ˜32,000

TABLE 2 Structures of Poly(arylene ethers) 1a-1c prepared from UllmannReaction Sym- Polymer synthesized bol

1a

1b

1c

Poly(arylene ether) 1a contains a 2-substituted thiophene as Ar₁ and a2,5-disubstituted thiophene as Ar₂. Poly(arylene ether) 1b contains a2-substituted pyridine as Ar₁ and a 3,5-disubstituted pyridine as Ar₂.Poly(arylene ether) 1c contains a 2-substituted pyridine as Ar₁ and a2,6-disubstituted pyridine as Ar₂.

The average molecular weight (MW) of each polymer was determined using aWaters HPLC system with three Phenomenex phenogel 5 micron mixed bedcolumns. One mg of polymer was dissolved in 10 ml of THF (HPLC grade).One hundred microliters of a 0.5 micron filtered solution was injectedinto the system and a refractive index (RI) detector was used to monitorthe mobile phase. A Gel Permeation Chromatography (GPC) spectrum of RIvs. time was obtained and MW was determined by comparing the GPCspectrum with a measurement performed using narrow MW polystyrenestandards.

The thermal stability of each polymer was studied by thermogravimetricanalysis (TGA) using a TA instrument, TGA 2960. Approximately 5 to 10 mgof a finely divided polymer powder was heated from room temperature to1000° C. in a ceramic cell at a linear heating rate of 10° C./minute.Heating was done in dry air and nitrogen with a flow rate of 75cm³/minute.

The glass transition (Tg) of each polymer was determined by differentialscanning calorimetry (DSC) using a TA instrument, DSC 2920. About 5 to10 mg of finely divided polymer powder was enclosed in a hermetic pan.The hermetic pan containing the polymer and a reference hermetic panwere placed into the cell which was then heated at a linear heating rateof 10° C./minute in nitrogen. Heat flow of the polymer vs. temperaturewas recorded and processed with a Universal Analysis program.

Dielectric constant of each polymer was measured using a TA instrument,DEA 2970 Dielectric Analyzer. The mode function used in the instrumentwas parallel plate mode. All measurements were done in a nitrogenenvironment. Finely divided polymer powder was pressed into a pelletwith a diameter of 25 mm and a thickness of 0.1 to 0.6 mm. The forceused to press the pellet was 12 tons. The pellet was placed betweenparallel plate sensors and a sinusoidal voltage was applied.Permittivity (dielectric constant) of the polymer vs. temperature wasrecorded and processed using the Universal Analysis program.

EXAMPLE 1 Synthesis of Poly{Arylene ether} 1a

In a 50 ml flask, 0.06 gm (0.61 mmol) of copper(I) chloride was added to0.6 ml of quinoline contained under a nitrogen blanket. The mixture wasstirred at 25° C. for 48 hours. A mixture of 1 gm (2.86 mmol) of9,9-bis(4-hydroxyphenyl)fluorene, 2.5 gm of toluene and 5 gm ofbenzophenone was charged to a 50 ml, 3-necked, round bottom flask fittedwith a distillation set, magnetic stirrer and thermometer. The mixturewas heated to 60° C. with stirring and in a nitrogen environment. Afterhomogeneity had been reached, 0.263 gm (5.72 mmol) of aqueous sodiumhydroxide solution was added dropwise to the mixture. A water azeotropewas then collected by vacuum distillation at an elevated temperature.After complete dehydration and removal of toluene, the reaction mixturewas cooled to room temperature and the distillation set was replaced bya condenser. The reaction mixture was then heated to 80° C. and 0.69 gm(2.86 mmol) of 2,5-dibromothiophene was added. The reaction mixture wasthen heated to 180° C. and a 0.6 ml portion of copper(I)chloride/quinoline catalyst was added. The reaction mixture wasmaintained at 180° C. for 17 to 24 hours at which time most of thedisodium salt of 9,9-bis(hydroxyphenyl)fluorene had gone into solution.A 0.02 gm portion of dry copper(I) chloride powder was added to thereaction mixture. The reaction temperature was increased to 190° C. andmaintained for 24 hours. A 0.3 gm portion of 2-bromothiophene was added.After 1 hour, the reaction mixture was cooled to 100° C. and 5 gm oftoluene was added. The reaction was then quenched in a rapidly stirredsolution of acetic acid and methanol. The precipitate obtained was firstSoxhlet-extracted with methanol for 24 hours followed by acetone foranother 24 hours. Finally, the precipitate was Soxhlet-extracted usingchloroform. The volume of the chloroform extract was reduced andreprecipitated in 100 ml of methanol. The polymer obtained was driedunder vacuum at 70° C. overnight to obtain a yield of between 10% and50%.

Those skilled in the art will recognize that other aromatics such asanthracene, terphenyl, and naphthalene, can be substituted for9,9-bis(hydroxyphenyl)fluorene to obtain thermally stable poly(aryleneethers) with a low k value that are useful in the present invention.

While this invention has been particularly shown and described withreference to, the preferred embodiments thereof, it will be understoodby those skilled in the art that various changes in form and details maybe made without departing from the spirit and scope of this invention.

1. A dual damascene method comprising: (a) providing a substrate inwhich a conductive layer has been formed; (b) forming sequentially astack of layers on said substrate including a passivation layer at thebottom of said stack followed by a dielectric layer, a first etch stoplayer, a second dielectric layer and a second etch stop or cap layer inwhich one or more layers in said stack is comprised of a poly(aryleneether) comprising the structure;

 wherein n=5 to 10000; and monovalent radical Ar₁ and divalent radicalAr₂ are heteroaromatic groups that incorporate O, N, Se, S, or Te orcombinations of the aforesaid elements; (c) forming a via hole and atrench in said stack of layers, said via hole is aligned above saidconductive layer and said trench is above said via hole; and (d)depositing a barrier metal layer and a metal layer within said via andtrench followed by planarizing said metal layer to be coplanar with thetop of said stack.
 2. The method of claim 1 wherein Ar₁ is a2-substituted pyridine and Ar₂ is a 3,5-disubstituted pyridine.
 3. Themethod of claim 1 wherein Ar₁ is a 2-substituted pyridine and Ar₂ is a2,6-disubstituted pyridine.
 4. The method of claim 1 wherein Ar₁ is a2-substituted thiophene and Ar₂ is a 2,5-disubstituted thiophene.
 5. Themethod of claim 1 wherein said poly(arylene ether) is furthercharacterized as having a thermal stability of about 350° C. or greater.6. The method of claim 1 wherein Ar₁ and Ar₂ are selected from the groupcomprised of;


7. The method of claim 1 wherein said poly(arylene ether) is furthercharacterized as having a dielectric constant of less than
 3. 8. Themethod of claim 1 wherein the 9,9-bis(hydroxyphenyl) fluorene group isreplaced by anthracene, phenanthrene, naphthalene, terphenyl or otheraromatic groups that form a poly(arylene ether) with a low dielectricconstant of less than 3 and a thermal stability to about 350° C. orgreater.
 9. The method of claim 1 wherein said poly(arylene ether) isdissolved in an organic solvent and spin coated to form a layer having athickness between about 1000 and 15000 Angstroms.
 10. The method ofclaim 9 wherein said poly(arylene ether) layer is baked between 50° C.and 250° C. for a period of from 0.5 to 30 minutes followed by curing ina furnace or by rapid thermal annealing at a temperature between 200° C.and 400° C. for a period of from 5 to 120 minutes.